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1.
E. Ya. Paryev 《Physics of Atomic Nuclei》2010,73(12):2035-2047
In the framework of the nuclear spectral function approach for incoherent primary proton-nucleon and secondary pion-nucleon
production processes we study the inclusive Λ(1520)-hyperon production in the interaction of 2.83-GeV protons with nuclei.
In particular, the A and momentum dependences of the absolute and relative Λ(1520)-hyperon yields are investigated within the different scenarios
for their in-medium width. Our model calculations show that the pion-nucleon production channel contributes distinctly to
the “low-momentum” Λ(1520) creation both in light and heavy nuclei in the chosen kinematics and, hence, has to be taken into
consideration on close examination of the dependences of the Λ(1520)-hyperon yields on the target mass number with the aim
to get information on their width in the medium. They also demonstrate that both the A dependence of the relative Λ(1520)-hyperon production cross section and momentum dependence of the absolute Λ(1520)-hyperon
yield at incident energy of interest are appreciably sensitive to the Λ(1520) in-medium width, which means that these observables
may be an important tool to determine the above width. 相似文献
2.
We investigate short-range correlations in nuclear and hypernuclear matter. Self-energies due to short-range correlations
and their influence on the nucleon and Λ -hyperon spectral functions are described in an approach accounting for a realistic
treatment of mean-field dynamics and a self-consistently derived quasi-particle interaction. Landau-Migdal theory is used
to derived the short-range interaction from a phenomenological Skyrme energy density functional, subtracting the long-range
pionic contributions to the nucleonic spectral functions. We discuss our results for different hyperon-baryon ratios to show
the influence of strangeness on the correlations in hypernuclear matter. 相似文献
3.
T.Yu. Tretyakova D.E. Lanskoy 《The European Physical Journal A - Hadrons and Nuclei》1999,5(4):391-398
Properties of light neutron-rich Λ hypernuclei (16
ΛC, 12
ΛBe, and 11
ΛLi) are calculated within the Skyrme-Hartree-Fock approach. Interplay between hypernuclear interaction features and properties
of these hypernuclei is studied. Response of weakly bound neutron states to hyperon addition depends generally on core distortion
by hyperon, and it is essentially different for the different states. This response is especially sensitive to details of
the ΛN interaction for 1p
1/2 states. Implications of the nuclear spin-orbit potential and nuclear incompressibility in the neutron-rich system properties
are inferred. Dependence of the Λ binding energies in hypernuclei on Z at fixed A is discussed.
Received: 16 December 1998 相似文献
4.
Scales in nuclear matter: Chiral dynamics with pion nucleon form factors<Superscript>⋆</Superscript>
N. Kaiser M. Mühlbauer W. Weise 《The European Physical Journal A - Hadrons and Nuclei》2007,31(1):53-60
A systematic calculation of nuclear matter is performed which includes the long-range correlations between nucleons arising
from one- and two-pion exchange. Three-body effects from 2π exchange with excitations of virtual Δ(1232)-isobars are also
taken into account in our diagrammatic calculation of the energy per particle ˉ(k
f). In order to eliminate possible high-momentum components from the interactions we introduce at each pion-baryon vertex a
form factor of monopole type. The empirical nuclear matter saturation point, ρ0 ≃ 0.16fm^-3, ˉ0 ≃ - 16MeV, is well reproduced with a monopole mass of Λ ≃ 4πf
π ≃ 1.16GeV. As in the recent approach based on the universal low-momentum NN potential V
low-k, the inclusion of three-body effects is crucial in order to achieve saturation of nuclear matter. We demonstrate that the
dependence of the pion exchange contributions to ˉ(k
f) on the “resolution” scale Λ can be compensated over a wide range of Λ by counterterms with two “running” contact couplings.
As a further application we study the in-medium chiral condensate 〈ˉq〉(ρ) beyond the linear density approximation. For ρ ⩽ 1.5ρ0 we find small corrections from the derivative dˉ(k
f)/dm
π, which are stable against variations of the monopole regulator mass Λ. 相似文献
5.
W. Cassing L. Jarczyk B. Kamys P. Kulessa H. Ohm K. Pysz Z. Rudy O.W.B. Schult H. Ströher 《The European Physical Journal A - Hadrons and Nuclei》2003,16(4):549-561
The lifetime of the Λ-hyperon in heavy hypernuclei measured in proton-Au, -Bi and -U collisions by the COSY-13 Collaboration
at COSY-Jülich has been analyzed to yield τΛ = (145±11) ps. This value for τΛ is compatible with the lifetime extracted from antiproton annihilation on Bi and U targets, albeit much more accurate. Theoretical
models based on the meson exchange picture and assuming the validity of the phenomenological ΔI = 1/2 rule predict the lifetime of heavy hypernuclei to be significantly larger (2-3 standard deviations). Such large differences
indicate that at least one of the assumptions in these models is not fulfilled. A much better reproduction of the lifetimes
of heavy hypernuclei is achieved in the phase space model, if the ΔI = 1/2 rule is discarded in the nonmesonic Λ decay.
Received: 8 August 2002 / Accepted: 20 December 2002 / Published online: 25 March 2003
RID="a"
ID="a"e-mail: h.stroeher@fz-juelich.de
Communicated by Th. Walcher 相似文献
6.
E. Ya. Paryev 《Physics of Atomic Nuclei》2012,75(12):1523-1535
In the framework of the nuclear spectral function approach for incoherent primary photon-nucleon and secondary pion-nucleon production processes we study the inclusive ??(1520)-hyperon production in the interaction of 2-GeV photons with nuclei. In particular, the A and momentum dependences of the absolute and relative ??(1520)-hyperon yields are investigated in two scenarios for its in-medium width. Our model calculations show that the pion-nucleon production channel contributes appreciably to the ??(1520) creation at intermediate momenta both in light and heavy nuclei in the chosen kinematics and, hence, has to be taken into consideration on close examination of the dependences of the ??(1520)-hyperon yields on the target mass number with the aim to get information on its width in the medium. They also demonstrate that the A and momentum dependences of the absolute and relative ??(1520)-hyperon production cross sections at incident energy of interest are markedly sensitive to the ??(1520) in-medium width, which means that these observables may be an important tool to determine the above width. 相似文献
7.
Z. Rudy W. Cassing L. Jarczyk B. Kamys P. Kulessa O.W.B. Schult A. Strzałkowski 《The European Physical Journal A - Hadrons and Nuclei》1999,5(2):127-129
It is shown that the mass dependence of the Λ-lifetime in heavy hypernuclei is sensitive to the ratio of neutron-induced
to proton-induced non-mesonic decay rates R
n/R
p. A comparison of the experimental mass dependence of the lifetimes with the calculated ones for different values of R
n/R
p leads to the conclusion that this ratio is larger than 2 on the confidence level of 0.75. This suggests that the phenomenological
ΔI= 1/2 rule might be violated for the nonmesonic decay of the Λ-hyperon.
Received: 31 March 1999 相似文献
8.
Axial mass in quasielastic antineutrino-nucleon scattering accompanied by strange-hyperon production
Reactions of quasielastic Λ-, Σ−-, and Σ0-hyperon production in antineutrino-nucleon interactions are studied. An axial-mass (M
A
) value that agrees with a fit to all accelerator data on exclusive and inclusive νN and νN reactions was extracted from a global statistical analysis of experimental data on differential and total cross sections
for ΔY = 0 and 1 quasielastic reactions of neutrino and antineutrino scattering on various nuclear targets. 相似文献
9.
Mahmood Mian 《Pramana》1993,41(2):145-149
The binding energy of the double hypernucleus
ΛΛ
6
is calculated in α + 2Λ cluster model using the method of translation invariant basis TIMO. As regards the required interaction
potentials we use a density dependent effective ΛN force and a gaussian form for ΛΛ potential. With these interactions a very reasonable value ofB
ΛΛ is obtained if the oscillator states up to the excitation quantum numberN=12 are taken into account in the expansion of wavefunction of the hypernucleus. This value ofN is much smaller than that obtained in an earlier study. This lowering inN value is attributed to a much better choice of ΛN potential used in the present study. 相似文献
10.
N. S. Malyshev G. V. Golubkov M. G. Golubkov R. J. Buenker H. P. Lieberman 《Russian Journal of Physical Chemistry B, Focus on Physics》2011,5(6):931-939
The potential curves of the nl(2Λ) electronically excited states of the K**-He quasimolecule (n, l, and Λ are the principal quantum number, angular momentum, and its projection on the molecular axis) are calculated. To describe
the interaction of the weakly bound electron with the singly charged potassium ion and the ground-state helium atom (with
taking into account their long-range electrostatic interactions), the formalism of two-center scattering theory and the finite-range
pseudopotential method are used. A comparison with the results of calculations performed by the MRD CI method is carried out.
The findings showed that, for small principal quantum numbers n, these methods complement each other, because the first is more reliable for large interatomic distances, R ≥ n, whereas second for small, R < n. The characteristic features of the behavior of the potential curves of the K**-He quasimolecule at large n and l are discussed. 相似文献
11.
T. Kadowaki J. Asai W. Imoto S. Iwata M. Kurosawa K. Nakai A. Sato K. Imai H. Takahashi C.J. Yoon T. Maruta M. Ieiri T. Nagae H. Noumi T. Fukuda P.K. Saha B. Bassalleck 《The European Physical Journal A - Hadrons and Nuclei》2002,15(3):295-298
In order to study the hyperon-nucleon spin-orbit interaction, asymmetries of the polarized Σ+ elastic scattering on protons have been measured. The polarized hyperons were produced through the p(π+, K+) Σ+ reaction in a liquid-scintillator active target, and tracks of Σ+p scattering events were recorded with a newly developed track detector named SCITIC (scintillating track image camera). Although
analyses of 10 times more data with more sophisticated data-taking systems and more elaborated analyzing tools are under way,
data from an early stage of this experiment indicate a large Σ+p spin-orbit interaction in contrast to the case of the small ΛN spin-orbit interaction.
Received: 27 May 2002 / Accepted: 23 July 2002 / Published online: 19 November 2002
RID="a"
ID="a"e-mail: nakai@post.kek.jp
Communicated by Th. Walcher 相似文献
12.
A spin-dependent interaction in hadrons is considered in the approach of the QCD string. The string moment of inertia, which
ensures the correct (inverse) Regge slope 2πσ, is found to suppress the spin-orbit interaction. For light quarks and moderate
angular momenta, the suppression constitutes around 25%, whereas for large angular momenta the spin-orbit interaction is suppressed
by the factor L
−2/5. For heavy quarks, the effect manifests itself as a string correction for the spin-dependent potential.
The text was submitted by the authors in English. 相似文献
13.
Khin Swe Myint S. Shinmura Y. Akaishi 《The European Physical Journal A - Hadrons and Nuclei》2003,16(1):21-26
The significance of ΛΛ-Ξ N coupling in double-Λ hypernuclei has been studied. The Pauli suppression effect due to this coupling
in 6
ΛΛ He has been found to be 0.43MeV for the coupling strength of the NSC97e potential. This indicates that the free-space ΛΛ
interaction is stronger by an about 5° phase shift than that deduced from the empirical data of 6
ΛΛ He without including the Pauli suppression effect. In 5
ΛΛ He and 5
ΛΛ H, an attractive term arising from the ΛΛ-Ξ N conversion is enhanced by the formation of an alpha-particle in the intermediate
Ξ states. According to this enhancement, we have found that the ΛΛ binding energy ( ΔB
ΛΛ) of 5
ΛΛ He is about 0.27MeV larger than that of 6
ΛΛ He for the NSC97e coupling strength. This finding deviates from the general picture that the heavier is the core nucleus,
the larger is ΔB
ΛΛ.-1
Received: 17 July 2002 / Accepted: 27 September 2002 / Published online: 17 January 2003
RID="a"
ID="a"e-mail: akaishi@post.ket.jp
Communicated by A. Molinari 相似文献
14.
We try to determine phenomenologically the extent of in-medium modification of σ-meson parameters so that the saturation observables
of the nuclear matter equation of state (EOS) are reproduced. To calculate the EOS we have used Brueckner-Bethe-Goldstone
formalism with Bonn potential as two-body interaction. We find that it is possible to understand all the saturation observables,
namely, saturation density, energy per nucleon and incompressibility, by incorporating in-medium modification of σ-meson-nucleon
coupling constant and σ-meson mass by a few per cent. 相似文献
15.
J. Haidenbauer 《The European Physical Journal A - Hadrons and Nuclei》2007,33(3):287-290
We present a new model for the hyperon-nucleon (ΛN , ΣN interaction, derived within the meson exchange framework. The model incorporates the standard one-boson exchanges of the
lowest pseudoscalar and vector meson multiplets with coupling constants fixed by SU(6) flavor symmetry relations. As a new feature, the contribution in the scalar-isoscalar (σ sector is derived from a microscopic
model of correlated ππ and Kˉ exchange. The same model is also used to constrain the interaction resulting from the vector-isovector (ρ exchange channel.
Additional short-ranged ingredients of the model in the scalar-isovector (a0) and scalar-isospin-1/2 (κ channels are likewise viewed as arising from meson-meson correlations but are treated phenomenologically.
With this model a satisfactory reproduction of the available hyperon-nucleon data is achieved. 相似文献
16.
R. L. Thews 《The European Physical Journal A - Hadrons and Nuclei》2006,29(1):15-18
We examine the possibility to utilize in-medium charmonium formation in heavy-ion interactions at collider energy as a probe
of the properties of the medium. This is possible because the formation process involves recombination of charm quarks which
imprints a signal on the resulting normalized transverse momentum distribution containing information about the momentum distribution
of the quarks. We have contrasted the transverse momentum spectra of J/ψ, characterized by 〈p
T
2〉, which result from the formation process in which the charm quark distributions are taken at opposite limits with regard
to thermalization in the medium. The first uses charm quark distributions unchanged from their initial production in a pQCD
process, appropriate if their interaction with the medium is negligible. The second uses charm quark distributions which are
in complete thermal equilibrium with the transversely expanding medium, appropriate if a very strong interaction between charm
quarks and medium exists. We find that the resulting 〈p
T
2〉 of the formed J/ψ should allow one to differentiate between these extremes, and that this differentiation is not sensitive to variations
in the detailed dynamics of in-medium formation. We include a comparison of predictions of this model with preliminary PHENIX
measurements, which indicates compatibility with a substantial fraction of in-medium formation. 相似文献
17.
《The European Physical Journal A - Hadrons and Nuclei》2007,33(3):265-268
An event emitting a Σ- -hyperon from a Ξ- -hyperon nuclear capture at rest has been observed in a hybrid-emulsion experiment. The event has been analyzed as the first
observation of the weak decay of the S = - 2 system. 相似文献
18.
Final state interaction effects inpp→ pΛK
+ andpd →3Heη reactions are explored near threshold to study the sensitivity of the cross-sections to thepΛ potential and theηN scattering matrix. The final state scattering wave functions between Λ andp andη and3He are described rigorously. The Λ production is described by the exchange of one pion and aK-meson between two protons in the incident channel. Theη production is described by a two-step model, where in the first step a pion is produced. This pion then produces anη by interacting with another nucleon 相似文献
19.
The KNΛ and KNΣ coupling constants have been calculated in the framework of the Chiral Bag Model(CBM). We find −3.88 ≤g
KNΛ≤−3.67 and 1.15 ≤g
KNΣ≤ 1.24 by taking into account pseudoscalar mesons (π, K) and vector mesons (ρ, ω, K
*) field effects. Particularly, it is shown that vector mesons make significant contributions to the coupling constants g
KNΛ and g
KNΣ. Our values are existing within the experimental limits compared to the phenomenological values extracted from the kaon photoproduction
and kaon-nucleon scattering experiments. Also, form factors are suggested for the πNN, πNΔ, KNΛ and KNΣ couplings.
Received: 17 August 1998 / Revised version: 22 December 1998 相似文献
20.
The NA60 experiment has studied low-mass muon pair production in In–In collisions at 158 A GeV with unprecedented precision. With these results there is hope that the in-medium modifications of the vector meson spectral
function can be constrained more thoroughly than before. We investigate in particular what can be learned about collisional
broadening by a hot and dense medium and what constraints the experimental results put on in-medium mass shift scenarios.
The data show a clear indication of considerable in-medium broadening effects but disfavor mass shift scenarios where the
ρ-meson mass scales with the square root of the chiral condensate. Scaling scenarios which predict at finite density a dropping
of the ρ-meson mass that is stronger than that of the quark condensate are clearly ruled out since they are also accompanied
by a sharpening of the spectral function.
PACS 25.75.-q 相似文献